Impacts of film mulching and increased nitrogen fertilization on the soil micro-food web

Film mulching and increased nitrogen fertilization profoundly affect soil ecosystem functioning and stability. The soil micro-food web, comprising diverse nematode-microbe interactions, plays a crucial role in mediating nutrient exchanges and energy flows. However, the effects of plastic film mulching (PFM) and elevated nitrogen fertilization on soil micro-food web dynamics remain poorly understood. In a long-term field trial, we evaluated these impacts using a two-factor design with mulching conditions (with (+PFM) and without (−PFM) plastic film) and three nitrogen fertilizer dosages (0 (N₀), 135 (N₁₃₅), and 270 kg N ha⁻¹ yr⁻¹ (N₂₇₀)). Soil sampling was conducted at three maize growth stages: seedling, jointing, and filling. The results revealed that +PFM led to notable declines in species richness and ecological network connectivity within the soil micro-food web, compared to −PFM. Compared to N₂₇₀, N₀ resulted in a markedly greater biomass carbon content in the soil micro-food web. A significantly lower soil micro-food web connectance was observed in N₂₇₀ than in N₀. The nematode channel ratio was significantly higher under N₂₇₀ than under N₀. Principal component analysis demonstrated that nitrogen fertilization intensity significantly altered soil physicochemical properties. Redundancy analysis revealed that soil temperature and ammonium nitrogen were the dominant factors driving micro-food web restructuring. Structural equation modeling clarified that the alteration of soil micro-food web under plastic film mulching was driven by fluctuations in soil temperature and ammonium nitrogen status. High nitrogen fertilizer input suppressed micro-food web development via ammonium nitrogen accumulation. Overall, long-term plastic film mulching and excessive nitrogen fertilization adversely affect the diversity, stability, and ecological functioning of soil biotic communities.